Thrust film cartridges utilizing film door light traps have been disclosed as an alternative to conventional film cartridges utilizing plush light traps. Typical thrust film cartridges include an outer shell having a longitudinally-extending opening for allowing for the exit of film from the cartridge. A cartridge spool is rotatably positioned within the outer shell to accommodate a roll of film. A film door is rotatably mounted adjacent the opening and is movable between a closed position, wherein a light tight seal is formed, and an open position, wherein film is allowed to exit the cartridge.
Thrust film cartridges are particularly useful for allowing rewinding and subsequent reloading of the film before the complete roll of film is used. Cameras having the ability to rewind and reload partially-used rolls of film are sometimes referred to as mid-roll interrupt cameras. Such a camera is disclosed in commonly-assigned U.S. Pat. Nos. 4,947,197 to Smart et al. and 4,965,600 to Smart et al., which are incorporated in their entirety herein by reference.
Unlike conventional film cartridges, thrust film cartridges have no film leader extending out of the cartridge to indicate that the film is unexposed. Consequently, some other means is necessary to provide an indication of whether unexposed frames exist on the film contained within the film cartridge. One such means is a visual exposure indicator visible to the camera user from the exterior of a film cartridge, as disclosed in various forms in commonly-assigned U.S. Pat. Nos. 4,994,833 to Cocca, 5,321,455 to Cocca, 5,030,978 to Stoneham et. al. and 5,032,854 to Smart et. al., which are incorporated in their entirety herein by reference. Generally, the visual exposure indicator is disposed on a film spool contained within the film cartridge and useful icons are disposed on the exterior of the film cartridge. Thus, the film spool can be rotated to align the visual exposure indicator with the appropriate visual icon. For example, a visual exposure indicator, such as an arrow, can be aligned with icons on the exterior of the film cartridge, for example, the letters U (for "unexposed"), P (for "partially exposed") or E (for "exposed") to provide the camera user a visual indication of the exposure condition of the film within the cartridge. Similarly, film cartridges can be provided with icons designating the "unexposed" and "exposed" exposure statuses. Additionally, other visual indicators can be used with other icons to indicate useful film information, including whether the film contained within the film cartridge has been processed. Aligning the visual indicator or indicators occurs by stopping film spool rotation when the visual indicator or indicators are aligned with the appropriate visual icon.
Generally, other operations involving the film spool and/or film cartridge, including for example, positioning the film spool to align the visual indicator or indicators, are referred to as "parking" the film spool.
The film cartridges disclosed by the above-referenced patents have a radial bar code disposed on a data disk positioned at an axial end of the film cartridge. The data disk is rotatable with the rotation of the film spool contained within the film cartridge during film advancement and rewind. The radial bar code represents information concerning the film contained within the film cartridge, including, among other things, the film speed, film type and total number of frames on the film. The radial bar code is typically read by the use of an optical sensor disposed adjacent to the radial bar code. As the position of the icons on the film cartridge are fixed relative to the positioning of the film cartridge within a loading chamber, the radial bar code, in conjunction with the optical sensor, can be used to park the film spool.
Generally, the film spool is parked after the film has been completely rewound into the film cartridge and before the film cartridge is made available to the camera user. However, the above identified patents make no provision as to determining when the film is completely rewound about the film spool contained within the film cartridge so that parking of the film spool can take place. It is therefore desirable to provide a mechanism and method, that will cooperate with a film cartridge having a radial bar code contained on a data disk and a means for parking a film spool, for determining when the film is completely rewound and for initiating film spool parking after the film has been completely rewound. It would be desirable to provide a simple, inexpensive mechanism and method for determining that the film is completely rewound before initiating film spool parking. It would be advantageous to use existing camera elements, dedicated to other camera functions, to accomplish the tasks of determining when the film is completely rewound and initiating film spool parking.